WebUSB is a new web standard, and is currently supported by Google Chrome, Microsoft Edge, and Opera browsers. Chrome browser is preferred, and has been tested on Chrome OS, Windows, Mac OS, and Android platforms.
The following boards are recommended.
Users have also reported having success with a wide variety of boards, like LILYGO TTGO T-Watch 2020, and Sipeed MaixCube (yes it works on Kendryte K210 too). In theory, any MicroPython board with USB to UART bridge should work. If you have a different board, please give it a try.